Method and means for preventing cavitation in hydraulic piston and vane pumps



24, 1965 w. H. TINKER ETAL 3,202,101

METHOD AND MEANS FOR PREVENTING CAVITATION IN HYDRAULIC PISTON AND VANEPUMPS Filed July 5, 1963 4 Sheets-Sheet 1 v w L L I i Z In 9 INVENTOR.

WALTER H. TINKER DARBY B. NEFF BY JOHN F. HEDGE WOOD, HERRON 8| EVANSAug. 24, 1965 w. H. TINKER ETAL 3,202,101

METHOD AND MEANS FOR PREVENTING CAVITATION IN HYDRAULIC PISTON AND VANEPUMPS 4 Sheets-Sheet 2 Filed July 5, 1963 77 68 ill/ill fig- J5INVENTORS WALTER H. TINKER DARBY B. NEFF BY JOHN F. HEDGE WOOD, HERRON aEVANS Aug. 24, 1965 w. H. TINKER ETAL METHOD AND ME 3,202,101 ANS FORPREVENTING CAVITATION IN HYDRAULIC PISTON AND VANE PUMPS 4 Sheets-Sheet5 Filed July 5, 1963 3 lmwlm.

my w i m &\\\\\\\\\\\\\\\\\\\\\\ Ru INVENTOR.

WALTER H. TINKER DARBY B. NEFF BY JOHN F. HEDGE WOOD, HERRON 8 EVANS g-1965 w. H. TINKER ETAL 3,202,101

METHOD AND MEANS FOR PREVENTING CAVITATION IN HYDRAULIC PISTON AND VANEPUMPS 4 Sheets-Sheet 4 Filed July 5, 1965 INVENTOR. WALTER H. TINKERDARBY B- NEFF BY JOHN F. HEDGE WOOD, HERRON 8 EVANS United States Patent3,202,101 METHOD AND MEANS FOR PREVENTING CAVITATION IN HYDRAULIC PISTONAND VANE PUMPS Walter H- Tinker, Frankfort, Darby B. Nelf, Worthington,and John F. Hedge, Columbus, Ohio, assignors to American Brake ShoeCompany, New York, N.Y., a corporation of Delaware Filed July 5, 1963,Ser. No. 293,081 17 Claims. (Cl. 103-5) This invention relates topositive displacement pumps of the piston and/or vane type for pumpingliquids.

A main object of the invention is to teach those skilled in the art anew concept and method for preventing cavitation in such pumps as wellas to provide means whereby the concept and method may be carried out.

It has long been recognized that one of the principal factors limitingthe speed, and hence delivery volume, of positive displacement pumps isthe tendency of such pumps to cavitate as their speed is increased. Moreparticularly, vane and piston type pumps can in general be characterizedas having liquid transfer or transporting cavities (i.e. inter-vanespaces andindividual cylinder bores) which are rotated in a plane.Liquid is introduced into these spaces through an inlet or low pressureport and it is transported and placed under pressure in the transportcavity as the cavity is rotated and is discharged through an outlet orhigh pressure port. Objectionable cavitation occurs in these pumps astheir speed is increased even when the best methods and means heretoforeavailable for introducing liquid into the cavities from the inlet sideof the pump are employed. When cavitation occurs, there is noise,vibration and frequently rapid erosion of the surrounding metal surfacesoccurs. Cavitation is further objectionable because it limits the speedat which the pump may be efiiciently operated.

In the past it has been proposed to inhibit cavitation by superchargingthe liquid on the inlet side of the pump. Supercharging, or increasingthe pressure on the inlet side of the pump, has not provided acompletely satisfactory solution to the problem for several reasons. Oneof the principal defects with supercharging is that its effectivenessvaries with pumping speed. Thus, a supercharger which will inhibitcavitation when the pump is operated in one speed range may beineifective to prevent cavitation in another speed range.

A principal object of the present invention is to teach a novel methodand provide a novel means for introducing liquid into the transportcavities of positive displacement pumps, and the like, so as toeliminate cavitation over extremely Wide and theoretically infinitespeed ranges. As a result, pumps made in accordance with this inventioncan be operated at much higher speeds than are now posisible and, infact, the upper speed limits are no longer limited by the problem ofcavitation, but rather by unrelated mechanical problems.

More particularly, the present invention is predicated upon the conceptof forceably directing the liquid as it is introduced into the transportcavity in such a manner that the velocity of the liquid relative to thecavity is in substantially an axial, or filling, direction. Inaccordance with the principles of the present invention, thisprerotation velocity is applied to the liquid by means of a rotator,preferably in the nature of a paddle wheel, disposed in a prerotationchamber intermediate the inlet line and rotating pump elements andclosely adjacent the latter. The rotator is driven at the same rate ofspeed as the pump elements and is effective to rotate the liquid at thisrate of speed. As a result, the liquid is moved in an oblique pathhaving a tangential component, which is the same as the tangentialcomponent of the rotating pump member and liquid transport cavities. Theliquid also has a second component which is axial relative to thesecavities. It is this latter component which causes the liquid to flowinto the cavities. Viewed in another way, to the rotating liquidtransport cavities,-the inlet liquid appears to be flowing straight intothe cavities. As a consequence, the liquid is introduced into the transport cavities with optimum eificiency and the absolute pressure withinthe cavities is always maintained well above the cavitation point.

One important advantage of the means for carrying out the prerotationconcept involved in this invention is that it is self-compensating,i.e., is not speed sensitive. More particularly, as was indicated above,the preferred embodiment of the prerotation means'includes a rotat-orwhich is rotated at the same rate of speed as the fluid transportcavities. This is readily eilected by mounting the pump elements androtator upon the same shaft. The rotat-or includes radially extendingelements which impart a rotational velocity to the liquid equal to therotational velocity of the liquid transport cavities. Since the rotatorand pump elements are driven together, the rotational velocities of theliquid and transport cavities are maintained substantially equal for anyspeed at which the pump is driven.

Another advantage of the present invention is that it absorbs only aminor amount of energy from the main pump drive shaft. Moreover, thissmall amount of energy required to drive the rotator is more thancompensated for by the increase in pump efiiciency attributable to theelimination of cavitation.

A still further advantage of the present invention is that it isrelatively economical to produce and install and, if desired, can beattached as a unit to pumps not originally provided with suchprerotation means.

It is a further object of the present invention to control more closelythe velocity vector of the liquid by combining with the rotatordescribed above, a guide ramp formed on the housing wall. This guideramp is angulated at the desired vector angle and directs the liquidinto the cavities so that the liquid moves substantially axiallyrelative to the cavities as explained above.

These and other objects and advantages of the present invention will bemore readily apparent from the following detailed description of thedrawings illustrating pre FIGURE 5 is :a cross sectionalview taken alonglines 5- 5 of FIGURE 4.

FIGURE 6 is an end view of a rotator.

FIGURE 7 is an elevation-a1 view of the rotator of FIGURE 6.

FIGURE 8 is an axial cross sectional view of a vane type pump providedwith a modified prerotation device constructed in accordance with theprinciples of the present invention.

FIGURE 9 is an end view of a modified form of r-otator.

FIGURE 10 is a cross sectional view taken along lines 10-40 of FIGURE 9.

FIGURE 11 is an elevational view of the modified rotator of FIGURE 9.

FIGURE 12 is a cross sectional view taken along lines 12--12 of FIGURE8.

FIGURE 13 is a cross sectional view taken along lines 1313 of FIGURE 12.

FIGURE 14 is a cross sectional view taken along lines 14-14 of FIGURE 8,and

FIGURE 15 is a cross sectional view taken along lines 1515 of FIGURE 4.

' The drawings illustrate two different types of positive displacementpumps provided with dynamic prerotation means of the present invention.More particularly, FIG- URE 1 shows a piston-type pump provided with aprerotation unit 11 and FIGURE 8 shows a vane-type pump 12 including amodified prerotation unit 13. It is to be understood that theseembodiments are merely exemplary and it is contemplated that the presentdynamic prerotation principles can also be applied to other positivedisplacement fluid energy translating devices.

- More particularly, as is shown in FIGURE 1, pistontype pump 10comprises a casing 14 having a body section 15 and a head member 16. Oneend of body section 15 abuts a port block 17 of the dynamic prerotationunit 11. The end of this port block 117 remote from the body section 15carries an end plate 16 having a threaded inlet port 20.

- Head member 16 and body section 15 cooperate to form a chamber 21.This chamber includes an annular area 22 for receiving a roller bearing23. This bearing rotatably journals cylinder barrel 24. Cylinder barrel24 loosely engages a shaft 25 and is connected for rotation with theshaft in any suitable manner, such as by means of loose splines at 26.It will be understood that shaft 25 is rotated by a suitable drive motor(not shown). The barrel member 24 is spring urged axially of shaft 25into abutting relation with a port plate 27 by means of a coil spring28. This coil spring is compressed between a shoulder 30 formed on thesplined portion of shaft 25 and an annular nut member 31 which surroundsshaft 25 and threadably engages the inner walls of a bore 32 formed inbarrel member 24.

The cylinder barrel 24 is provided with a plurality, for example seven,of longitudinally extending cylindrical bores 33. These bores arepreferably equispaced about the circumference of a circle andcommunicate with openings 34 extending inwardly from the face of thecylinder barrel 24 in abutment with port plate 27. Openings 34 aredisposed to be brought into alternate registration with the arcuateinlet and outlet ports 35 and 36 formed in port, plate 27. Each of thecylindrical bores 33 houses a piston 37 mounted for reciprocatingmovement within the cylinder. The reciprocating movements of thesepistons function to draw fluid into the cylindrical bores when theopenings 34 are in registry with the inlet port 35 and to dischargefluid from the cylindrical bores when the openings 34 are in registrywith the outlet port 36.

Reciprocating movements of pistons 37 are effected by means of a camassembly 38 mounted upon head member 16. This cam assembly includes anangulated swash plate 40 carried by head member 16. The angulated camsurface 41 of the swash plate is engaged by bearing shoes 42 mountedupon the ends of the pistons 37. Specifically, each of the pistons 37 isprovided with a spherical head member 43. This head member is mountedwith a socket formed in one of the pistons. It is to be understood thatthe socket is clamped around the head so that the shoes are effective totransmit both a pushing and a pulling force upon the pistons. Each ofthe bearing shoes 42 passes through an opening formed in a retainerplate 44. This plate abuts flanges 45 formed on the shoes and iseffective to maintain the shoes in engagement with swash plate 40.Retainer plate 44 is rotatably journalled in a bearing 46 carried by asleeve 47. The sleeve threadably engages an opening in swash plate 4-0.This opening is.

Shaft 25, to which cylinder barrel 24 is connected, is rotatablyjournalled in suitable journal bearings (not shown) carried by headmember 16. The shaft passes through a center opening formed in portplate 27 into a chamber 48 formed in port block 17. This end of theshaft carries a rotator member 56 which is keyed to the shaft as bymeans of key 51 and is retained in place by a retainer ring 52. Rotator50 thus rotates at all times with shaft 25 and hence with cylinderbarrel 24.

As is explained in detail below, rotator 50 functions in conjunctionwith the configuration of chamber 48 to impart a rotative movement tothe fluid so that the velocity vector of the fluid at the inlet port 35contains substantially the same tangential component as the opening 34of the cylinder barrel moving in registry with the inlet port. Thus,substantially the only movement of the fluid relative to the opening 34is an axial or cylinder filling movement.

More particularly, the details of construction of rotator 50 are bestshown in FIGURES 1, 6 and 7. As there shown, the rotator comprises acylindrical hub 53 which fits over shaft 25. The rotator is furtherprovided with a plurality of radial blades 54. On the inlet side of therotator (the side adjacent inlet port 29), these blades are ofrelatively short radius, i.e., substantially equal to the radius of theinlet port. An annular ring 55 is secured to the outer ends of theseblades in any suitable manner, such as by brazing.

In the center section of the rotator, radial blades 54 are ofsubstantially greater length. As shown in FIGURE 1, these blades are ofa length such that the tips of the blades are at a radial distance fromthe axis of shaft 25 substantially equal to the maximum radial distancefrom the axis of bores 33. A second sleeve 56 is secured to the outerends of the blades at the center portion of the rotator. At thedischarge side of the rotator, radial arms 45 are tapered inwardly as at57 toward hub 53.

Port block 17, which encloses rotator 50, is a casting which is providedwith a center chamber 48 in communication with inlet port 21) coaxialwith shaft 25. Block 17 also includes a threaded outlet port 58connected through a tapered conduit section 60 to outlet port 36 of portplate 27. Block 17 is maintained in correct angular alignment With theport plate 27 by means of locating pin 61 and is held in engagement withbody member 15 by means of bolts 62.

The portion of chamber 48 adjacent to inlet port 20 is of considerablylarger diameter than the inlet port 20. However, the effective size ofthe chamber 48 adjacent the inlet end of rotator 56 is reduced tosubstantially the diameter of the rotator by means of annular ring 63which surrounds the rotator. formed on block 17 and is held in place asby means of bolts 65. Chamber 48 also includes an enlarged annular area66 for accommodating the large diameter portion of the rotator adjacentto sleeve 56. Block 17 is also provided with an annular shoulder 67disposed on the opposite side of annular space 66 from ring 63, theinner diameter of this shoulder being substantially equal to the innerdiameter of sleeve 56.

Block 17 further includes a ramp section 68 adjacent to the leading edge70 of inlet port 35. This ramp section 68 is located in quadrants I andW of FIGURE 4. It is to be understood that in one preferred embodiment,the block 17 is formed symmetrical about vertical center line 71 so thata second ramp 68a is formed adjacent to the trailing edge 72 of inletport 35.

Since the ramps 68 and 68a are mirror images, only ramp 68 will bedescribed in detail. Specifically, the discharge end of chamber 48includes a tapered peripheral wall 73 located diametrically opposite anannular opening 74 in communication with inlet port 35 of the portplate. This tapered wall 73 merges in quadrant 1 with ramp section 63.The ramp section 68 lies in a transverse plane which is always radial tothe center Ring 63 abuts a shoulder 64 the center line at an angle 6'.

axis 75 of shaft 25. The longitudinal extent of the ramp 68 lies on anangle from its line of merger with tapered wall 73 to the leading edge76 of opening 74.

The relation between the angle of this ramp and the desired resultantvector of liquid flow is best shown in FIGURES 3 and 5. Specifically, asis shown in FIGURE 3, when cylinder barrel 24 and hence piston chambers33 are rotated by shaft 25, this rotation causes each piston chamber tohave a tangential vector K. At the same time that the piston chamber 33is rotating, its associated piston 37 is reciprocated. During the intakeportion of the pumping cycle, the piston is, retracted axially with avector U. Theoretically, it is desirable that the liquid should enterthe piston cylinder with the same vector '6. In order that the liquidwill have only a movement relative to the cylinder 33 which is axial,the liquid must actually move along the resultant vector movement of thepiston 37, i.e. in accordance with vector I?) which equals 1+7]. It isnoted that vector E makes an angle 0 with the axis of the pistoncylinder 33 (and with any line parallel to the center axis 75). Thevector E represents the absolute velocity of the liquid entering theport 35 and cylinder 33.

In the prerotation unit of FIGURE 1, the rotator 50 imparts to theliquid a tangential vector substantially equal to the tangentialcylinder velocity vector K and an axial velocity component vectorsubstantially equal to the piston vector 6. As is shown in FIGURE 5,ramp 68 is angulated with respect to a line parallel to Angle 0' istheoretically equal to angle 0. In practice, however, the angle 6' ismade slightly larger than angle 6 and the absolute value of theresultant liquid flow vector /1 3 is slightly greater than the absolutevalue of the resultant piston movement vector l 3 to compensate forliquid velocity losses due to friction.

As is shown in FIGURES 4 and 15, the discharge end of the block 17further includes an arcuate rim section 77. This rim section lies alongthe inner radial edge of arcuate opening 74 and ramp sections 68 and68a. This rim assists in channelling liquid flow along the ramp section68 and through port 74.

It will be appreciated that the prerotation unit just described iseffective to provide the desired axial liquid flow relative to therotating piston cylinders 33 for all speeds at Which the pump isoperated. Specifically, both the cylinder barrel 24 and rotator 50 aredirectly driven by shaft 25. Consequently, these members move at exactlythe same speed. Additionally, the outer radius of the rotator, adjacentsleeve 56, is substantially equal to the maximum radial distance of thecylinder bores 33 from center line 75. Thus, the rotator is at all timeseifective to impart to the liquid, a rotating or tangential vector Kequal to the corresponding vector movement K of the piston cylinders.Moreover, the velocity of piston reciprocation (vector 6) variesdirectly with the angular rotative speed. Thus, the resultant vectormovement of the piston F is always in the same relative direction andthe angle 0 between this vector and a line parallel to axis 75 remainsconstant. The rotator is effective to provide the requisite tangentialvector K and the pressure differential between atmosphere and cylinders33 is effective to provide the requisite axial com- 6 construction ofthis vane type pump, except for the prerotation unit 13, is the same asthe pump disclosed in Blasutta et al. Patent No. 2,924,182 for FluidPressure Energy Translating Device, and to which reference is made for acomplete description of details not herein described.

Essentially, pump 12 comprises a casing, or housing, of generallycylindrical configuration. The housing 80 includes a cylindrical sidewall 81 and an end wall 82. These walls define a hollow cylindricalchamber 83 in which a rotary vane type pump 84 is mounted. Housingmember 80 is provided with a boss 85 including a tapered, radiallyextending, exhaust or high pressure passageway 86. This passagewayterminates at its inner end in a port 87 in fluid communication withchamber 83. The opposite end of passageway 86 communicates with aninternally threaded hollow flange 88. This flange is secured to housingmember 80 by suitable bolts (not shown). It is to be understood that thehigh pressure side of a hydraulic circuit is connected to fitting 88.

The end of chamber 83 remote from outlet conduit 86 is closed by meansof a cap member 90. This cap member is secured in abutment with the endof housing member 80 by means of a plurality of mounting bolts 91. Cover90 includes a tapered inlet conduit which is coaxial with main driveshaft 99. Conduit 92 communicates at one end With a prerotation. chamber93 and at the other end with a boss 94. Boss 94 is internally threadedin a manner similar to boss 88 and is secured to the cap member 90 inany suitable way, such as by means of bolts (notshown). This boss 94 isadapted to be connected to the low pressure side of the hydraulicsystem.

The pump assembly 84 comprises two rigid cylindrical check, or port,plates 95 and 96. These port platesare disposed in abutting relationwith opposite sides of a cam ring 97 so that the cam ring is in efiectsandwiched between the cheek plates. The two cheek plates 95 and 96 andcam ring 97 are locked in a predetermined angular relation to oneanother and to cap member 90 by means of a longitudinally extending pin(not shown) extending through aligned openings in the cheek plates, camring and cap. i

Cheek plates 95 and 96 and cam ring 97 define a rotor chamber whichreceives a rotor assembly ,198; the rotor assembly including a rotorbody 100 of generally cylindrical configuration. This r-otor body isprovided with a plurality of equispaced, radially extending vane slots101. Each of these slots slidably receives avane member 102. Varies 102are urged radially outwardly by means of springs 103 compressed betweenopposed sockets formed. in the vanes and rotor body. The rotor body 100is mounted upon shaft 99. This shaft extends out wardly through an endwall 82 .of. the casing and passes through aligned central openings incheek plates 95 and 96. Shaft 99 is rotatably journalled in a bearing(not shown) carried by end Wall 82 and by a bearing 104 mounted Withincheek plate 96. Rotor body 100 is mounted for rotation with shaft 99 bymeans of a loose ponent G. Since the ramp angle 0' is substantiallyequal to the desired resultant vector angle 6', the prerotation unitalways supplies liquid to ports 34 at the optimum vector angle andvelocity so that relative to the piston chambers 33 the liquid appearsto be moving in a substantially axial direction. Thus, irrespective ofpump speed the cylinders 33 are filled each time they pass inlet port 35and no cavitation occurs.

. A vane type pump 12 provided with a modified form of prerotationdevice 13 is shown in FIGURE 8. The

spline connection indicated at 105.

It will be appreciated that as the rotor body rotates, the tips of thevanes 102 are maintained in a sealing engagement with the inner surfaceof cam ring 97. As is described in detail in the above mentionedBlasutta patent, cam ring 97 forms the outer peripheral wall of therotor chamber. This peripheral wall includes two diametrically opposedsealing portions disposed at equal radii from the axis of shaft 99 andtwo diametrically opposed transfer portions of equal, but, larger, radiithan the sealing portions. The radii .of these transfer portions arelikewise struck from the axis of shaft 99 which is also the axial centerof the rotor chamber. Adjacent arcuate sealing and transfer portions ofthe peripheral wall of the rotor chamber are interconnected by ramps;

Cheek plate 96, as is shown in FIGURES Sand 12-14,

is provided with an annular shoulder 106 which abuts a cooperatingshoulder formed on cap 90. The opposite surface of the cheek plate abutscam ring 97 and is slidably engaged by rotor body 100 and vanes 102.Cheek plate 96 includes two diametrically opposed liquid inlet, suctionor low pressure passageways 167 and 108 which communicate with theprerotation chamber 93 in cap 90 andextend from that chamber to theinterior of rotor chamber 83. The inlet passageways 107 and 108terminate in elongated arcuate inlet ports 110 and 111 formed in theface or wall of the cheek plate immediately adjacent to'the rotorassembly 98.

As is further shown in FIGURES l2 and 14, cheek plate 96 furtherincludes a pair of passageways 112 and 113 which connect the inlet,suction or low pressure passageways 107 and 108 with elongated ports 114and 115 formed in the face of the cheek plate in registry with the innerends of the vane slots in the rotor body as the vanes are rotatedpastthe ports.

It will thus be. apparent that the path of liquid to the rotor chamberof pump 84 is through flange 94 to prerotation chamber 93, from thatchamber through passageways 107 and 108 and ports 11%) and 111 into therotor chamber. Liquid also flows through a plurality of axiallyextending bores 116 formed in cam ring 97. These bores conduct liquidfrom inlet ports 110 and 111 to corresponding inlet'ports 117 and 118formed in cheek plate 95. Bores 116 are also eifective to conduct liquidto ports 120 and 121'corresponding to ports 115 and 114. It is tobeunderstood that the inlet ports 110 and 111, 117 and 118 are disposedgenerally in registry with ramp sections interconnecting the sealingportions of the Cam ring with the transfer portions in the mannerexplained in detail in Blasutta Patent No. 2,924,182.

Cheek plate 95 is provided with two diametrically pposed exhaust ports(not shown) centered in a diametral line disposed at right angles to thediametral line passing through the centers of inlet ports 110 and 111.These latter high pressure outlet or exhaust ports are in fluidcommunication with a'relatively large peripheral groove 122. This groovein turn communicates with outlet port 87 and through that port andflange 88 to the high pressure side of the system. Plate 95 alsoincludes two inner arcuate ports which are connected to the main outletports and are disposed radially inwardly of the outlet ports. Theseinner ports are disposed for registry with the inner ends of the vaneslots as the slots move past the outlet ports. It is to be understoodthat the outlet ports and inlet ports in cheek plate 95 are disposed onopposite sides of the rotor from corresponding ports 123, 124, 125 and126 formed in cheek plate 96. As is explained in detail in the Blasuttapatent, these outlet ports are also in registry with a second set oframps interconnecting the transfer sections and sealing sections of camring 97.

In operation, as. liquid is introduced into the rotor chamber throughinlet ports 110 and 111, the liquid passes into a confined pocketdefined by two adjacent vanes, the adjacent peripheral wall section ofring 97 and rotor body 100. The liquid is trapped in this pocket and istransferred from the inlet ports across the transfer sections to theoutlet ports. The liquid then flows through these outlet ports, andconduit 122 to port 87 and flange 88' The function of prerotation unit13 is to impart to the liquid entering the prerotation chamber 93 frominlet 94 a rotational velocity substantially identical with that of theindividual inter-vane pockets or chambers as they pass the inlet ports.The liquid also has an axial component which tends to cause liquid toflow into the pockets due to the pressure diiferential betweenatmosphere and the low pressure in the vanepockets. The resultant liquidflow vector in the prerotation chamber is such that relative to themovingvane pockets the liquid has only this axial component. In short,the vector relationship between the, liquid flow and vane pockets islike that described above in connection withjthepiston pump embodiment.

The details of construction of the rotator 127 for imparting the desiredrotation to the liquid are best shown in FIGURES 8-11. As there shown,rotator 127 includes a hub portion 128 mounted upon a shaft extensionbolt 130. This extension is coaxial with shaft 99 and is threadablysecured to the shaft as at 131. Rotator 127 is keyed to extension shaft139 as by means of key 132 and is held in place by means of a nut member133 threaded over the end of extension shaft 139. Rotator 127 furthercomprises a plurality of radially extending, outwardly tapering blades134. These blades are formed integral with the hub and are equispacedfrom one, another as is best shown in FIGURE 9. The leading face of therotator, i.e. the face disposed toward inlet conduit 92 is provided witha fluid guiding wall 135. This wall has a narrow diameter portion 136forming a continuation of conduit 92. The wall curves outwardly intoproximity with peripheral wall 137 of cap member 98. Peripheral wall 137in turn tapers slightly outwardly in the direction of the pump chamber83. The maximum diameter of prerotation chamber 93 is slightly greaterthan the maximum diameter of inlet ports 111} and 111.

Rotator 127 is directly connected to' main drive shaft 99 so that therotator is always driven at the same rate of speed as rotor assembly 98.Since the maximum diameter of the rotator is slightly greater than themaximum diameter of the liquid inlet ports even after friction losses,the rotator is effective for all speeds \of the pump to impart to theliquid a rotational or tangential velocity component vectorsubstantially the same as the corresponding component vector of the vanepockets Thus, the entering liquid is always moved relative to the vanepockets in a substantially longitudinal, or feeding, direction andcavitation is eliminated at all pump speeds.

From the above disclosure of the general principles of the presentinvention and the description of two detailed embodiments, those skilledin the art will readily co-mprehend various modifications to which theinvention is susceptible as well as the manner in which prerotationunits can be utilized in conjunction with other positive displacementfluid energy translating devices including, for example, piston and vanetype motors; Accordingly, we desire to be limited only by the scope ofthe following claims. a

Having described our invention, we claim:

1. Amethod of introducing liquid into a positive displacement hydraulicfluid energy translating device of the type having a plurality of liquidtransporting cavities rotatable in a plane, said method comprising thesteps of causing said liquid to flow along an inlet path generallyperpendicular to the plane of rotation of said liquid transportingcavities, and simultaneously impart ing a rotational velocity to saidliquid, said rotational velocity being in the same direction as thedirection of rotation of said liquid transporting cavities,therotational velocityof said liquid having a tangential componentsubstantially equal to the rotational velocity of the liquidtransporting cavities so that the only relative movement between theliquid transport cavitiesv and liquid is in a path substantiallyperpendicular to the plane of rotation of-said liquid transportingcavities.

2. A method of introducing liquid into'a positive dis-I the type havinga plurality of liquid transporting cavities rotatable in a plane, saidmethod comprising the steps of creating a sub-atmospheric pressure insaid cavities causingsaid liquid to flow in response to the dilferentialbetween atmospheric pressure and said subatmospheric pressure along aninlet path generally perpendicular to the plane of rotation of saidliquid transporting cavities, and simultaneously bringing said liquidinto contact with a rotating'rnember for imparting arotational velocityto said liquid,'said rotational velocity being in thesame direction asand substantially equal in magnitude to the rotational velocity of saidcavities.

3. A method of introducing liquid into a positive displacement hydraulicfluid energy translating device of the type having a plurality of liquidtransporting cavities rotatable in a plane, said method comprising thesteps of causing said liquid to flow along an inlet path generallyperpendicular to the plane of rotation of said liquid transportingcavities, passing said liquid through a rotating rotator forsimultaneously imparting a rotational velocity to said liquid, saidrotational velocity having substantially the same tangential componentas the velocity of said liquid transporting cavities.

4. In a hydraulic fluid energy translating device of the positivedisplacement type having an inlet side, an outlet side, a plurality offluid transporting cavities and means for rotating said cavities aboutan axis in a plane, the improvement which comprises a dynamicprerotation unit disposed on the inlet side of said fluid energytranslating device, said dynamic prerotation unit comprising a housingincluding a chamber in communication with said cavities, a hollowrotator having radially extending vanes, mounted within said housing,and means for rotating said rotator about the axis of rotation of saidcavities and in the direction of rotation of said fluid transportingcavities, said fluid flowing through said rotator, said rotator beingeflective to impart a rotational component to the velocity of saidfluid, said rotational component being in the same direction as thedirection of rotation of said fluid transporting cavities, said housingbeing configurated to establish ax-ial communication between saidrotator and said fluid transporting cavities, whereby fluid flowingthrough said rotator enters said cavities with substantially the samevelocity imparted by said rotator.

5. In a hydraulic fluid energy translating device of the positivedisplacement type having an inlet side, an outlet side, a plurality offluid transporting cavities, and means for rotating said cavities aboutan axis in a plane, the improvement which comprises a dynamicprerotation unit disposed on the inlet side of said fluid energytranslating device, said dynamic prerotation unit comprising a housingincluding a chamber in communication with said cavities, a rotatormounted within said housing, and means for rotating said rotator aboutthe axis of rotation of said cavities and in the direction of rotationof said fluid transporting cavities, said rotator being eflective toimpart a rotational component to the movement of said fluid, saidcomponent being in the same direction as the direction of rotation ofsaid fluid transporting cavities, and angulated ramp means formed insaid housing chamber for directing said fluid in a predetermineddirection relative to said cavities, said housing being configurated toestablish axial communication between said rotator and said fluidtransporting cavities, whereby fluid flowing through said rotator enterssaid cavities with substantially the same velocity imparted by saidrotator.

6. In a hydraulic fluid energy translating device of the positivedisplacement type having an inlet side, an outlet side, a plurality oftransporting cavities and means for rotating said cavities about an axisin a plane, the improvement which comprises a dynamic prerotation unitdisposed on the inlet side of said fluid energy translating device, saiddynamic prerotation unit comprising a housing including a chamber incommunication with said cavities, a hollow rotator having radiallyextending planar vanes, means mounting said rotator Within said housingcoaxial with the axis of rotation of said cavities, and means forrotating said rotator in the same direction and at the same speed assaid transporting cavities, said rotator being eflective to impartsubstantially the same rtational velocity to the said fluid as therotational velocity of the cavities, said housing being configurated toestablish axial communication between said rotator and said fluidtransporting cavities, whereby fluid flowing through 10 said rotatorenters said cavities with substantially the same velocity imparted bysaid rotator.

7. In a hydraulic fluid energy translating device of the positivedisplacement type having an inlet side, an outlet side, a plurality offluid transporting: cavities and means for rotating said cavities in aplane, the improvement which comprises a dynamic prerotation unitdisposed on the inlet side of said fluid energy translating device, saiddynamic prerotation unit comprising a housing including a chamber incommunication with said cavities, a hollow rotator having radiallyextending vanes, means mounting said rotator within said housing c0-axial with the axis of rotation of said cavities, and means for rotatingsaid rotator in the same direction and at the same speed as saidtransporting cavities, said rotator being effective to impartsubstantially the same rotational velocity to the said fluid as therotational velocity of the cavities, said chamber being configurated toprovide axial communication between said rotator and said fluidtransporting cavities, and a ramp formed in the said chamber fordirecting said fluid toward said cavities, said ramp being angularlydisposed whereby the resultant velocity of said fluid relative to saidcavities as said fluid enters said cavities is substantially parallel tothe axis of rotation of said cavities.

8. In combination with a hydraulic vane type pump having a plurality ofradially extending spaced vanes having fluid transporting spacestherebetween, an inlet side and an outlet side, and means for rotatingsaid vanes about an axis in a plane, the improvement which comprises adynamic prerotation unit disposed on the inlet side of said pump, saiddynamic prerotation unit comprising a housing including a chamber incommunication with the spaces between said vanes, a rotator mountedWithin said housing, and means for rotating said rotator coaxially withthe rotation of said fluid vanes and in the direction of rotation ofsaid fluid vanes, said rotator being eflective to impart a rotationalcomponent to the velocity of said fluid, said rotational component beingin the same direction as the direction of rotation of said vanes, saidchamber being configurated to provide axial communication between saidrotator and the spaces between said vanes, whereby said fluid enterssaid spaces with substantially the same velocity imparted to it by saidrotator.

9. In combination with a hydraulic vane type pump having a rotor, aplurality of radially extending spaced vanes carried by said rotor andhaving fluid transporting spaces therebetween, an inlet side, an outletside, and means for rotating said vanes about an axis in a plane, theimprovement which comprises a dynamic prerotation unit disposed on theinlet side of said pump, said dynamic prerotation unit comprising ahousing including a chamber in communication with the spaces betweensaid vanes, a rotator mounted within said housing coaxially with saidrotor, and means for rotating said rotator coaxially with locity to saidfluid as the rotational velocity of said vanes, said chamber beingconfigurated to provide axial com munication between said rotatorand thespaces between said vanes, whereby said fluid enters said spaces withsubstantially the same velocity imparted to it by said rotator.

It). In combination with a hydraulic vane type pump having a rotor, aplurality of radially extending spaced vanes carried by said rotor andhaving fluid transporting spaces therebetween, an inlet side, an outletside, and means for rotating said vanes about an axis in a plane, theimprovement which comprises a dynamic prerotation unit disposed on theinlet side of said pump, said dy namic prerotation unit comprising ahousing including a chamber in communication with the spaces betweensaid vanes, a rotator mounted within said housing coaxially with saidrotor, and means for rotating said rotator at the same speed and in thesame direction as said fluid vanes, said rotator being effective toimpart substantially the same rotational velocity to said fluid as therotational velocity of said vanes, and an angulated ramp formed on thewall of said chamber for directing said fluid as it is discharged fromsaid rotator toward said vanes, said chamber being configurated toprovide axial communication between said rotator and the spaces betweensaid .vanes, whereby said fluid enters said spaces with substantiallythe same velocity imparted to it by said rotator, and whereby therelatve movement between said fluid and fluid transporting spaces issubstantially parallel to the axis of said rotor.

11. In combination with a hydraulic vane type pump having a rotor, aplurality of radially extending spaced vanes carried by said rotor andhaving fluid transporting spaces therebetween, an inlet side, an outletside, and a shaft supporting said rotor for rotating said vanes about anaxis in a plane, the improvement which comprises a dynamic prerotationunit disposed on the inlet side of said pump, said dynamic prerotationunit comprising a housing including a chamber in communication with thespaces between said vanes, a rotator mounted within said housing uponsaid rotor carrying shaft, said rotator being rigidly connected to saidrotor carrying shaft and being rotated at the same velocity as saidrotor, said rotator including a plurality of spaced radially extendingarms, said fluid flowing through said rotator which is effective toimpart a rotational component to the velocity of said fluid equal to therotational component of said vanes, said chamber being configurated toprovide axial communication between said rotator and the spaces betweensaid vanes, whereby said fluid enters said spaces with substantially thesame velocity imparted to it by said rotator.

12. In combination with a hydraulic vane type pump having a rotor, aplurality of radially extending spaced vanes carried by said rotor andhaving fluid transporting spaces therebetween, an inlet side, an outletside, and a shaft supporting said rotor for rotating said vanes about anaxis in :a plane, the improvement which com-prises a dynamicprerot'ation unit disposed on the inlet side of said pump, said dynamicprerotation unit comprising a housing including a chamber incommunication with the spaces between said vanes, a rotator mountedwithin said housing upon said rotor carrying shaft, said rotor being[rigidly connected to said rotor carrying shaft and being rotated at thesame velocity as said rotor, said rotator including a plurality ofspaced radially extending arms, said fluid flowing through said rotatorwhich is effective to impart a rotational component to the velocity ofsaid fluid equal to the rotational component of said vanes, and anangulated ramp formed on the wall of said chamber for directing saidfluid as it is discharged from said rotator toward said vanes, saidchamber being conligurated to provide axial communication between saidrotator and the spaces between said vanes, whereby said fluid enterssaid spaces with substantially the same velocity imparted to it by saidrotator, and whereby the relative movement between said fluid and fluidtransporting spaces is substantially parallel to the axis of said rotor.

13. In combination with a hydraulic piston type pump of the type havingan inlet side and an outlet side, a cylinder barrel, a shaft mountingsaid cylinder barrel for rotation about an axis, a plurality ofcylinders having axes parallel to said shaft, said cylinders beingdisposed along the circumference of a circle, a piston disposed withineach of said cylinders, and means for reciprocating said pistons as saidcylinder barrel is rotated, the improvement which comprises a dynamicprerotation unit disposed on the inlet side of said pump, said dynamicprerotatio-n unit comprising a housing including a chamber incommunication with said cylinders, a rotator mounted Within saidhousing, and means for rotating said rotator about the axis of rotationof said cylinder barrel in the direction of rotation of said cylinders,said rotator being elfective to impart a rotational component to thevelocity of said fluid, said rotational component being in the samedirection as the direction of rotation of said cylinder barrel, saidhousing being configurated :to establish axial communication betweensaid rotator and said cylinders, whereby fluid flowing through saidrotator enters said cylinders with substantially the same velocityimparted to it by said rotator.

1 In combination with a hydraulic piston type pump of the type having aninlet side, an outlet side, a cylinder barrel, a shaft mounting saidcylinder barrel for rotation about an axis, a plurality of cylindershaving axes parallel to said shafit, said cylinders being disposed alongthe circumference of a circle, a piston disposed within each of saidcylinders, and means for reciprocating said pistons as said cylinderbarrel is rotated, the improvement which comprises a dynamic prerotationunit disposed on the inlet side of said pump, said dynamic prerotationunit comprising a housing including a chamber in communication with saidcylinders, a rotator mounted within said housin and means for rotatingsaid rotator about the axis of rotation of said cylinder barrel at thesame speed and in the direction of rotation as said fluid cylinders,said rotator being effective to impart a rotational component to thevelocity of said fluid substantially equal to the rotational componentof the velocity of said cylinders, said rotational component being inthe same direction as the direction of rotation of said cylinder barrel,said housing being co-n figurated to establish axial communicationbetween said rotator and said cylinders, whereby fluid flowing throughsaid rotator enters said cylinders with substantially the same velocityimparted to it by said rotator.

15. In combination with a hydraulic piston type pump of the type havingan inlet side, an outlet side, a cylinder barrel, a shaft mounting saidcylinder barrel for rotation about an axis, a plurality of cylindershaving axes parallel to said shaft, said cylinder-s being disposed alongthe circumference of a circle, a piston disposed within each of saidcylinders, and means for reciprocating said pistons as said cylinderbarrel is rotated, the improvement which comprises a dynamic prerotationunit disposed on the inlet side of said pump, said dynamic prerotationunit comprising a housing including a chamber in communication with saidcylinders, a rotator mounted within said housing, and means for rotatingsaid rotator about the axis of rotation of said cylinder barrel at thesame speed and in the direction of rotation of said fluid cylinders,said rotator being effective to impart a rotational component to thevelocity of said fluid substantially equal to the rotational componentof the velocity of said cylinders, and ramp means formed on the wall ofsaid chamber for directing said fluid as it is discharged from saidrota-tor toward said cylinders, said rotational component being in thesame direction as the direction of rotation of said cylinder barrel,said housing being configurated to establish axial communication betweensaid rotator and said cylinders, whereby fluid flowing through saidrotator enters said cylinders with substantially the same velocityimparted to it by said rotator, and whereby the relative movementbetween said fluid and said cylinders is substantially parallel to saidshaft.

16. In combination with a hydraulic piston type pump of the type havingan inlet side, an outlet side, a cylinder barrel, a shaft mounting saidcylinder barrel for rotation about an axis, a plurality of cylindershaving axes parallel to said shaft, said cylinders being disposed alongthe circumference of a circle, a iston disposed within each of saidcylinders, and means for reciprocating said pistons as said cylinderbarrel is rotated, the improvement which comprises a dynamic prerotationunit disposed on the inlet side of said pump, said dynamic prerotationunit comprising a housing including a chamber in communication with thespaces between said cylinders,a rotator mounted within said housing uponsaid sha'ft, said rotator being rigidly secured to said shaft, wherebysaid rotator is rotated in the same direction and at the same speed assaid cylinder I barrel, said rotator comprising a plurality of spacedradially extending wanes in planes generally parallel to said shaft,said rotator being effective to impart the same rotational component tothe velocity of said fluid as the rotational component of saidcylinders, said rotational component being in the same direction as thedirection of rotation of said cylinder barrel, said housing beingcontigurated to establish axial communication between said rotator andsaid cylinders, whereby fluid flowing through said rotator enters saidcylinders with substantially the same velocity imparted to it by saidr'otator.

'17. In combination with a hydraulic piston type pump of the type havingan inlet side, an outlet side, a cylinder barrel, a shaft mounting saidcylinder barrel for rotation about an axis, a plurality of cylindershaving axes parallel to said shaft, said cylinders being disposed alongthe circumterence of a circle, a piston disposed within each of saidcylinders, and means for reciprocating said pistons as said cylinderbarrel is rotated, the improvement which comprises a dynamic prerotationunit disposed on the inlet side of said pump, said dynamic prerotationunit comprising a housing including a chamber in communication with thespaces between said cylinders, a ro-tator mounted 'within said housingupon said shaft, said rotator being rigidly secured to said shaft,whereby said rotator is rotated in the same direction and at the samespeed as said cylinder barrel, said rotator comprising a plurality ofspaced radially extending vanes in planes generally parallel to saidshaft, said rotator being eifective to impart the same rotationalcomponent to the velocity of said fluid as the rotational component ofsaid cylinders, and ramp means formed in the Wall Olf said chamber fordirecting said fluid as it is discharged from said rotat-or toward saidcylinders, said rotational component being in the same direction as thedirection of rotation of said cylinder barrel, said housing beingconfigurated to establish axial communication between said rotator andsaid cylinders, whereby fluid flowing through said rotator enters saidcylinders with substantially the same velocity imparted to it by saidrotator, and whereby the relative movement between said fluid and saidcylinders is substantially parallel to said shaft,

References Cited by the Examiner UNITED STATES PATENTS LAURENCE V.EFNER, Primary Examiner. ROBERT M. WALKER, Examiner.

4. IN A HYDRAULIC FLUID ENERGY TRANSLATING DEVICE OF THE POSITIVEDISPLACEMENT TYPE HAVING AN INLET SIDE, AN OUTLET SIDE, A PLURALITY OFFLUID TRANSPORTING CAVITIES AND MEANS FOR ROTATING SAID CAVITIES ABOUTAN AXIS IN A PLANE, THE IMPROVEMENT WHICH COMPRISES A DYNAMICPREROTATIOPN UNIT DISPOSED ON THE INLET SIDE OF SAID FLUID ENERGYTRANSLATING DEVICE, SAID DYNAMIC PREROTATION UNIT COMPRISING A HOUSINGINCLUDING A CHAMBER IN COMMUNICATION WITH SAID CAVITIES, A HOLLOWROTATOR HAVING RADIALLY EXTENDING VANES, MOUNTED WITHIN SAID HOUSING,AND MEANS FOR ROTATING SAID ROTATOR ABOUT THE AXIS OF ROTATION OF SAIDCAVITIES AND IN THE DIRECTION OF ROTATION OF SAID FLUID TRANSPORTINGCAVITIES, SAID FLUID FLOWING THROUGH SAID ROTATOR, SAID ROTATOR BEINGEFFECTIVE TO IMPART A ROTATIONAL COMPONENT TO THE VELOCITY OF SAIDFLUID, SAID ROTATIONAL COMPONENT BEING IN THE SAME DIRECTION AS THEDIRECTION OF ROTATION OF SAID FLUID TRANSPORTING CAVITIES, SAID HOUSINGBEING CONFIGURATED TO ESTABLISH AXIAL COMMUNICATION BETWEEN SAID ROTORAND SAID FLUID TRANSPORTING CAVITIES, WHEREBY FLUID FLOWING THROUGH SAIDROTATOR ENTERS SAID CAVITIES WITH SUBSTANTAILLY THE SAME VELOCITY BYSAID ROTATOR.